Not Applicable.
Not Applicable.
(1) Field of the Invention
The present invention relates to a fluorescent imaging thermographic method and system for use particularly in surface temperature measurements, which are reproducible over time. The invention provides a temperature-sensitive fluorescent probe comprising a rare earth compound in an ultraviolet and fluorescence transparent medium wherein the intensity of fluorescence varies as the temperature varies, in particular, probes comprising Europium(1,1,1,5,5,5-hexafluoroacetylacetone)3 for measuring temperatures greater than 24xc2x0 C., Terbium(1,1,1,5,5,5-hexafluoroacetylacetone)3 for measuring temperatures less than 24xc2x0 C., or both. The probe is applied as a layer to a surface, exposed to fluorescence-inducing energy, and the emitted fluorescence is captured as an image by a CCD camera. A novel ratio imaging algorithm enables the temperature at each location on the surface to be determined.
(2) Description of Related Art
The prior art has developed methods using fluorescence measurements to determine the temperature of a surface. The problem has been that the measurements have not been reproducible over time because of the photo-bleaching of the fluorescent probe.
U.S. Pat. No. 2,551,650 to Urbach discloses the measurement of temperature distributions on the surface of solid bodies using fluorescence emitting phosphors.
U.S. Pat. Nos. 4,075,493, 4,215,275, 4,448,547, and 4,560,286 to Wickersheim discloses a technique wherein an object or environment to be measured is provided with a phosphor material layer that emits at least two optically isolatable wavelength ranges whose intensity ratio depends upon the object or environment temperature. The technique uses optical system filters and signal processing to determine the temperature profile of the surface of the object. In particular embodiments, the emitted radiation is brought to the detector by an optical system, which may include an optical fiber.
U.S. Pat. No. 4,302,970 to Snitzer et al. discloses a temperature probe formed by an optical fiber having a core fabricated from a glass host doped with a trivalent rare earth such as europium positioned at the location where temperature is to be measured.
U.S. Pat. No. 4,374,037 to Takahashi discloses a method for preparing a divalent-europium-activated calcium sulfide phosphor comprising reacting a molten mixture consisting essentially of alkaline-earth-metal chloride and europium chloride with gaseous carbon disulfide at temperatures between 850xc2x0 C. and 1200xc2x0 C. for one to six hours.
U.S. Pat. No. 4,455,741 to Kolochner discloses a solid state electronic device that is optically monitored during fabrication to detect hot spots which are indicative of faulty operation. The surface temperature of the device is measured by applying a fluorescent material to the device and subsequently monitoring the temperature dependent fluorescence of the material.
U.S. Pat. No. 4,523,799 to Delhaye et al. discloses a device that optimizes the coupling of two optical systems for the observation and analysis of objects, one of the systems producing the illumination of a point on the object being studied while the other produces the image of that point in an analyzer.
U.S. Pat. Nos. 4,652,143 and 4,789,992 to Wickersheim et al. discloses an optical temperature measurement technique that utilizes the decaying luminescent intensity characteristic of a sensor composed of a luminescent material that is excited to luminescence by a light pulse or other periodic or other intermittent source of radiation. The luminescence emissions of a preferred sensor exhibit an approximately exponential decay with time that is the average of a distribution of chemically reproducible crystallites and are repeatable with a high degree of accuracy regardless of excitation level or prior temperature history of the sensor.
U.S. Pat. No. 4,708,494 to Kleinerman discloses methods and materials associated with remote optical measurements of temperatures with luminescent sensors.
U.S. Pat. No. 4,819,658 to Kolodner discloses a method and apparatus for measuring the temperature profile of a surface exhibiting spacial or temporal variations in temperature. The fluorescent material is applied in a layer less than 10 xcexcm in thickness and in thermal contact with the surface.
U.S. Pat. No. 5,149,972 to Fay et al. discloses an imaging apparatus, which includes a fluorescence imaging microscope, ultraviolet radiation source capable of producing a plurality of ultraviolet excitation wavelengths, a filter device to select a first and a second excitation wavelength from the plurality of ultraviolet excitation wavelengths, a sample chamber to hold a sample for illumination by the radiation of the first and second wavelengths, and a processor in communication with a photometer to record the intensity signal produced by the photometer.
U.S. Pat. No. 5,304,809 to Wickersheim discloses the use of a CCD camera to measure the image and luminescent signal from a fluorescent layer disposed on an object. The system further contains a computer for measuring the differences in transmissions and calculating the temperature of the object.
U.S. Pat. No. 5,435,937 to Bell et al. discloses a polymer material containing compounds, which are internally luminescent.
U.S. Pat. No. 5,618,732 to Pease et al. discloses a method of calibrating photo-activatable chemiluminescent matrices.
U.S. Pat. No. 5,705,821 to Barton et al. discloses a scanning fluorescence microthermal imaging apparatus and method. The apparatus focuses a laser onto a thin fluorescent film disposed over the surface of an integrated circuit. By collecting fluorescent radiation information from the film, and performing point-by-point data collection with a single-point photodetector, a thermal map of the integrated circuit is formed to measure any localized heating associated with defects in the integrated circuit.
U.S. Pat. No. 6,123,455 to Beshears et al. discloses an apparatus for measuring the temperature of a moving substrate which includes an air gun to spray controlled amounts of a powdered phosphor onto the moving substrate. A laser produces light pulses, and optics direct the light pulses onto the phosphor on the moving substrate, in response to which the phosphor emits luminescence with a decay rate indicative of the temperature of the phosphor. A photodetector detects the luminescence.
Crofcheck et al. (J. Polymer Sci: Part A: Polymer Chem. 33: 1735-1744 (1995)) discloses a method for monitoring the temperature of high speed cationic photopolymerizations using temperature-sensitive tris(xcex2-diketone) chelates of europium probes and detecting temperature-sensitive luminescence of the probes during the reaction. The method uses either europium(1,1,1,5,5,5-hexafluoroacetylacetone)3 or europium(benzoyl-1,1,1-trifluoroacetone)3 as the probe and measures the temperature of the photopolymerizations using a two-wavelength ratiometric method.
The present invention provides a fluorescent imaging thermographic method and system for use particularly in surface temperature measurements, which are reproducible over time. The invention provides a temperature-sensitive fluorescent probe comprising a rare earth compound in an ultraviolet and fluorescence transparent medium wherein the intensity of fluorescence varies as the temperature varies, in particular, provided are probes comprising Europium(1,1,1,5,5,5-hexafluoroacetylacetone)3 for measuring temperatures greater than 20xc2x0 C. or Terbium(1,1,1,5,5,5-hexafluoroacetylacetone)3 for measuring temperatures less than 20xc2x0 C., or both. The probe is applied as a layer to a surface, exposed to fluorescence-inducing energy, and the emitted fluorescence is captured as an image by a CCD camera. A novel ratio imaging algorithm enables the temperature at each location on the surface to be determined.
Therefore, the present invention provides a system for determining a temperature distribution of a surface exhibiting spatial, temporal, or combinations thereof variations in temperature where there is a layer on the surface with a temperature sensitive fluorescent material including a rare earth compound that is resistant to photo-bleaching over time in an ultraviolet and fluorescence transparent medium, wherein the material is in thermal contact with the surface, and wherein the fluorescence emission of the material varies as the temperature of the surface varies, which system comprises (a) light producing means for exposing the material to fluorescence-inducing energy over time as the temperature changes which induces the material to emit fluorescence at one or more visible wavelengths; (b) sensing means for detecting an image of the fluorescence induced by the fluorescence-inducing energy; (c) photodiode means for measuring fluctuations in the fluorescence-inducing energy during calibration of the system or during long exposure times of the material to the fluorescence-inducing energy source; and (d) computer means for processing the image from the camera means and the measurements from the photodiode means wherein the computer means determines the temperature distribution of the surface over time.
Preferably, the light producing means in the system produces is ultraviolet light.
Further it is preferable that the temperature distribution is produced by determining a relationship between the fluorescence intensity and the temperature for each location on the surface by establishing the calibration between either a ratio of broadband fluorescent intensity at an unknown temperature and at a known reference temperature for each location on the surface or a ratio of fluorescent intensities of at least two distinct wavelengths of fluorescence emission, whereby the ratio is an indication of the temperature for each location on the surface.
Further still, it is preferable that the transparent medium is selected from the group consisting of poly(methylmethacrylate), perdeutero-poly(methylmethacrylate), and mixture thereof.
Further still, it is preferable that the rare earth compound is a lanthanide(xcex2-diketone)3 chelate. Preferably, wherein the lanthanide(xcex2-diketone)3 chelate is selected from the group consisting of europium(1,1,1,5,5,5-hexafluoroacetylacetone)3, europium(benzoyl-1,1,1-trifluoroacetone)3, europium(6,6,7,78,8,8-heptafluooro-2,2-dimethyl-3,5-octanedionato)3, europium(2,2,6,6-tetramethyl-3,5-heptanedionato)3, terbium(1,1,1,5,5,5-hexafluoroacetylacetone)3, terbium(benzoyl-1,1,1-trifluoroacetone)3, terbium(6,6,7,78,8,8-heptafluooro-2,2-dimethyl-3,5-octanedionato)3, and terbium(2,2,6,6-tetramethyl-3,5-heptanedionato)3, and combinations thereof.
It is further preferred that in the system the sensing means is selected from the group consisting of a CCD camera, a CID sensor, and a CMOS sensor.
Further still, the present invention provides a system for determining a temperature profile of a surface exhibiting spatial, temporal, or combinations thereof variations in temperature of a layer including a temperature-sensitive fluorescent material selected from the group consisting of Europium(1,1,1,5,5,5-hexafluoroacetylacetone)3, terbium(1,1,1,5,5,5-hexafluoroacetylacetone)3, and combinations thereof in an ultraviolet and fluorescence transparent medium capable of being positioned on the surface wherein the fluorescence of the material varies as the temperature varies, which apparatus comprises (a) a light producing means for providing a fluorescence-inducing energy source for inducing the temperature-sensitive fluorescent material to emit fluorescence in one or more visible wavelengths, which are reproducible over time; (b) a sensing means for acquiring an image of the fluorescence; (c) a photodiode means for measuring fluctuations in the fluorescence-inducing energy during calibration of the apparatus or during long exposure times of the layer on the surface to the fluorescence-inducing energy source; and (d) a computer means for processing the image acquired by the camera means and the measurements from the photodiode means wherein the computer means determines the temperature distribution of the surface at each point in the image.
In a preferred embodiment, the light producing means produces ultraviolet light.
Preferably, in the system the temperature distribution is produced by determining a relationship between the fluorescence and the temperature for each location on the surface by establishing a calibration between either a ratio of broadband fluorescent intensity at an unknown temperature and at a known reference temperature for each location on the surface or a ratio of fluorescent intensities of at least two distinct wavelengths of fluorescence emission, whereby the ratio is an indication of the temperature for each location on the surface.
Further still, it is preferable that the medium is selected from the group consisting of poly(methylmethacrylate), perdeutero-poly(methylmethacrylate), and mixture thereof.
Further still, it is preferable that the sensing device is selected from the group consisting of a CCD camera, a CID sensor, and a CMOS sensor.
The present invention also provides a method for measuring a temperature distribution of a surface exhibiting spatial, temporal, or combinations thereof variations in temperature, comprising (a) providing a surface with a layer of a temperature-sensitive fluorescent material including a rare earth compound that is resistant to photo-bleaching over time in an ultraviolet and fluorescence transparent medium, wherein the material is in thermal contact with the surface, and wherein the fluorescence emission of the material varies as the temperature of the surface varies; (b) exposing the material to a fluorescence-inducing energy source which induces the material to emit fluorescence at one or more visible wavelengths over time; (c) detecting the induced fluorescence emission with a sensing device over time, which produces an image of the induced fluorescence, and measuring fluctuations in the fluorescence-inducing energy during calibration of the method and during long exposure times of the material on the surface to the fluorescence-inducing energy source with a photodiode; (d) determining the temperature distribution of the surface by establishing a calibration which defines quantitatively a relationship between fluorescence intensity and the temperature for each location on the surface wherein the calibration is either a ratio of broadband fluorescent intensity at an unknown temperature and at a known reference temperature for each location on the surface or a ratio of fluorescent intensities of at least two distinct wavelengths of fluorescence emission, whereby the ratio is an indication of the temperature for each location on the surface; and (e) measuring the temperature of the surface over time.
Preferably, in the method the fluorescence image and the fluorescence intensity are digitized and stored in a data buffer of a computer.
It is further preferable in the method that a computer program accesses the fluorescence image and the fluorescence intensity from the data buffer and processes the fluorescence image and the fluorescence intensity to produce the temperature distribution.
In a preferred embodiment of the method, the medium is selected from the group consisting of poly(methylmethacrylate), perdeutero-poly(methylmethacrylate), and mixture thereof.
It is further preferable that the rare earth compound is a lanthanide(xcex2-diketone)3 chelate. In particular, wherein the lanthanide(xcex2-diketone)3 chelate is selected from the group consisting of europium(1,1,1,5,5,5-hexafluoroacetylacetone)3, europium(benzoyl-1,1,1-trifluoroacetone)3, europium(6,6,7,78,8,8-heptafluooro-2,2-dimethyl-3,5-octanedionato)3, europium(2,2,6,6-tetramethyl-3,5-heptanedionato)3, terbium(1,1,1,5,5,5-hexafluoroacetylacetone)3, terbium(benzoyl-1,1,1-trifluoroacetone)3, terbium(6,6,7,78,8,8-heptafluooro-2,2-dimethyl-3,5-octanedionato)3, and terbium(2,2,6,6-tetramethyl-3,5-heptanedionato)3, and combinations thereof.
It is further preferable, that the fluorescence-inducing energy source is ultraviolet light.
Further still, it is preferable that the sensing device is selected from the group consisting of a CCD camera, a CID sensor, and a CMOS sensor.
The present invention further provides a method for measuring a temperature distribution of a surface exhibiting spatial, temporal, or combination thereof variations in temperature, comprising (a) providing on the surface with a layer of a temperature-sensitive fluorescent material selected from the group consisting of Europium(1,1,1,5,5,5-hexafluoroacetylacetone)3, terbium(1,1,1,5,5,5-hexafluoroacetylacetone)3, and combinations thereof in an ultraviolet and fluorescence transparent medium, wherein the material is in thermal contact with the surface, and wherein fluorescence emission of the material varies as the temperature of the surface varies; (b) exposing the material to fluorescence-inducing energy which causes the material to emit fluorescence in a visible wavelength; (c) detecting the fluorescence emission of the material over time; and (d) determining the temperature distribution of the surface over time.
Preferably, the fluorescence-inducing energy is ultraviolet light.
Further still, it is preferable that the medium is selected from the group consisting of poly(methylmethacrylate), perdeutero-poly(methylmethacrylate), and mixture thereof.
Further still, it is preferable that the temperature distribution is produced by determining a relationship between the fluorescence intensity and the temperature for each location on the surface by establishing a calibration between either a ratio of broadband fluorescent intensity at an unknown temperature and at a known reference temperature for each location on the surface or a ratio of fluorescent intensities of at least two distinct wavelengths of fluorescence emission, whereby the ratio is an indication of the temperature for each location on the surface.
Further still, it is preferable that the fluorescence induced by the fluorescence-inducing energy is detected as an image by a sensing device and a photodiode is provided for measuring fluctuations in the fluorescence induced by the fluorescence-inducing energy during calibration of the method or during long exposure times of the material on the surface to the fluorescence-inducing energy source. In particular, wherein the sensing device is selected from the group consisting of a CCD camera, a CID sensor, and a CMOS sensor.
Further still, it is preferable that the fluorescence image and the intensity are digitized and stored in a data buffer of a computer. In particular, wherein a computer program accesses the image from the data buffer and processes the image and the intensity to produce the temperature distribution.
It is an object of the present invention to provide a method and system for determining the temperature profile on a surface exhibiting spatial, temporal, or combinations thereof variations in temperature of a layer using a temperature-sensitive fluorescent material as a probe wherein the probe is resistant to photo-bleaching.